Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare this is a non-read-only, non-idempotent, non-destructive mutation, so the safety profile is covered. The description adds the ownership requirement and names the return ('The seat'), but says nothing about what happens to the previously primary character or whether the switch is reversible.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three compact fragments with the effect front-loaded and no filler. The telegraphic 'The character's own player. Returns: The seat.' reads slightly clipped, but nothing is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter mutation with annotations and no output schema, the definition covers the essentials. It leaves unclear what a 'seat' is, what happens to the prior primary, and whether any role or campaign permission is needed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and both parameters are documented with slug/id guidance in the schema itself. The description adds no syntax or format detail, only a hint that 'character' should be one you play; baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a concrete verb and resource: switching which of your characters is the one visible to the table, matching the title's 'primary' framing. It separates this from nearby tools like set_character_on_hud or set_character_overlay only implicitly, so an agent must infer that this changes a persistent primary designation rather than a display setting.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'The character's own player' implies a prerequisite that you may only promote a character you control, which is useful. It never states when to prefer this over assign_character, add_seat, or the HUD/overlay setters, and gives no when-not guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.